Vacuum in hydro electric power plants

[antekatavic]

2 questions. 1. why vacuum is not used in hydro electric power plants and 2. why water under presure from big depths are not used for revolving turbines?
1. with vacuum you would need only small amount of water faling from a big altitude to revolve turbine. Turbine would revolve faster and longer because there is no air resistence and also there would be no noise and corrosion.
2. if you put turbine and everything you need to produce electric in a some kind of submarine and went to a big depth of a sea,lake or a ocean and then every now and then let the water under presure revolve turbine, or maybe it is possible to relocate that water under presure to a surface where it will revolve turbine. If you take a big hose that is wide at the bootom of the sea and narrow at the surface and with a combination of the same way you suck up your petrol from a tank of a car maybe it would work.

 

[JaredJames]

1. with vacuum you would need only small amount of water faling from a big altitude to revolve turbine. Turbine would revolve faster and longer because there is no air resistence and also there would be no noise and corrosion.

It takes more energy to generate a vacuum than you get back from it.

2. if you put turbine and everything you need to produce electric in a some kind of submarine and went to a big depth of a sea,lake or a ocean and then every now and then let the water under presure revolve turbine, or maybe it is possible to relocate that water under presure to a surface where it will revolve turbine. If you take a big hose that is wide at the bootom of the sea and narrow at the surface and with a combination of the same way you suck up your petrol from a tank of a car maybe it would work.

That's not how siphoning works. The rest of this is nonsense.

If you filled a box with water at the bottom of the ocean, as you brought it to the surface the surrounding pressure would reduce and the box would expand (potentially exploding). Losing anything you gain from such a box. And that's before you consider the energy requirements for such a task.

Put simply, what you have outlined above would consume far more energy than they would generate, wouldn't improve efficiency of the processes and certainly wouldn't be economically viable.

 

[antekatavic]

but what if the water is under the turbine and that same water is going up the pipe hundreds of meeters and than coming down a narrow pipe and revolving the turbine... like some kind perpetum motion.

 

[JaredJames]

Uh, no.

The pressure gradient within the pipe would mean there would be no fluid flow.

Simply going from wide to narrow with the pipe will not induce a flow.

Perpetual motion machines don't exist, they can't exist, they are a banned subject here. Recommend you drop this before it continues.

 

[yoshtov]

remember that energy always balances out. if you narrow the pipe, you would increase the velocity of the water stream, but you would be decreasing the flow rate.

Also, mentioning perpetual motion on a physics forum is a bit like suggesting that there is no God on a Christian forum.

 

[berkeman]

but what if the water is under the turbine and that same water is going up the pipe hundreds of meeters and than coming down a narrow pipe and revolving the turbine... like some kind perpetum motion.

We do not waste time discussing perpetual motion machines here.


EDIT -- Instead, you can go here to read all about them: http://en.wikipedia.org/wiki/Perpetual_motion_machines

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